A student dissolves 14.8 g of ammonium nitrate (NH4NO2) in 300. g of water in a well-insulated open cup. He then observes the temperature of the water fall from 20.0°C to 15.0°C over the course of 4.3 minutes. Use this data, and any information you need from the ALEKS Data resource, to answer the questions below about this reaction: NH4NO3(s) → NH4+(aq) + NO3^- (aq)

Required:
a. Is this reaction exothermic, endothermic, or neither?
b. If you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in this case.

a. Endothermic

b. 6586J are absorbed.

Explanation:

a. When the reaction occurs, the temperature is decreasing from 20.0°C to 15.0°C, that means the reaction is absorbing heat and is endothermic.

b. To find the heat absorbed we must use:

Q = -m*ΔT*C

Where Q is change in heat,

m is the mass of solution (300g + 14.8g = 314.8g)

ΔT is change in temperature (15.0°C - 20.0° = -5.0°C)

And C is specific heat of the solution (4.184J/g°C assuming is the same heat than the heat of pure water).

Replacing:

Q = -314.8g*-5.0°C*4.184J/g°C

Q =

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answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol